1. Field of the Invention
The present invention relates to a polymer.
2. Discussion of the Background
A semiconductor device (e.g., IC and LSI) production process has utilized micro fabrication by means of lithography using a photoresist composition. Along with an increase in the degree of integration of integrated circuits, it has become necessary to form a sub-micron or quarter-micron fine pattern. Therefore, i-lines, KrF excimer laser light, or ArF excimer laser light having a short exposure wavelength has been used instead of g-lines. Lithography that utilizes electron beams, X-rays, or EUV light instead of excimer laser light has also been developed.
Lithography that utilizes electron beams or EUV light is considered to be next-generation or third-generation patterning technology, and requires a positive-tone resist that exhibits high sensitivity and high resolution. In particular, it is very important to increase sensitivity in order to reduce the wafer processing time. However, when increasing the sensitivity of a positive-tone resist that is used for electron beams or EUV light, a deterioration in resolution and nano edge roughness occurs. Therefore, development of a resist that achieves these properties in combination has been strongly desired. Note that the term “nano edge roughness” refers to a phenomenon in which the edge of the resist pattern irregularly changes with respect to the substrate in the direction perpendicular to the line direction due to the properties of the resist, so that a difference occurs between the design dimensions and the actual pattern dimensions when viewed from above. The difference from the design dimensions is transferred by etching using the resist as a mask, and causes a deterioration in electrical properties. As a result, yield decreases. In particular, it is very important to improve the nano edge roughness when forming a fine pattern having a line width of 0.25 μm or less. High sensitivity, high resolution, an excellent pattern shape, and a small degree of nano edge roughness have a trade-off relationship. It is very important to achieve these properties at the same time.
It is also important to achieve high sensitivity, high resolution, an excellent pattern shape, and a small degree of nano edge roughness at the same time when using lithography that utilizes KrF excimer laser light.
As a resist that is suitable for a lithographic process that utilizes KrF excimer laser light, electron beams, or EUV light, a chemically-amplified resist that utilizes an acid catalytic reaction has been mainly used from the viewpoint of increasing sensitivity. As a positive-tone resist, a chemically-amplified resist composition that mainly includes a phenolic polymer (phenolic acid-dissociable polymer) that is insoluble or scarcely soluble in an alkaline solution, but becomes soluble in an alkaline solution due to an acid, and an acid generator has been effectively used.
A resist composition that include a phenolic acid-dissociable polymer obtained by copolymerizing acid-dissociable acrylate monomers, and a compound (sulfonic acid generator) that generates sulfonic acid upon irradiation of active rays or radiation, has been known as such a positive-tone resist. Such positive-tone resist compositions are disclosed in, for example, U.S. Pat. No. 5,561,194, Japanese Patent Application Publication (KOKAI) No. 2001-166474, Japanese Patent Application Publication (KOKAI) No. 2001-166478, Japanese Patent Application Publication (KOKAI) No. 2003-107708, and Japanese Patent Application Publication (KOKAI) No. 2001-194792.